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  1. #1
    Senior Member Curt's Avatar
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    On the right track??

    Here's what I've gathered so far for a hammock that balances strength and low weight. I'm not worrying about the bug netting or fly for now - just the hammock.

    I need it to support 400 pounds. Unlikely to ever actually have that much in it, but me (big), my kid (little), and stuff could come close. It builds in a safe margin of error and seems to be a common number (Travel Hammock, ENO, etc.)

    So....

    Hammock fabric: 1.9oz ripstop nylon - buy 4 yards of 60-63". Use full width (halfway between a single and a double). Use 10 or 11 feet of length depending on how I do the ends. Make a few side pockets from the extra

    Tree straps: 1.5" webbing. Probably Speer's version. Nice and long to get around the Pacific Northwest's big trees. Do people just tie a loop in the end and run it through like a girth hitch?

    Rope/cord: 5mm seems to be strong enough for big loads with some room to spare. Rated to 1100 or 1200 lbs. Put a bight on the end and carabiner it to the webbing?

    Am I on the right track? Will that hold me up - assuming construction methods are appropriate and done right?

    Thanks!

    -Curt

  2. #2
    slowhike's Avatar
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    about the end of the webbing... you can tie it to form a loop (i've done that several times in the past) but fact is that the knot takes away from the strength of the webbing.
    so a much better way to form a loop at the end is to sew it w/ bar tacks. i make about 7 bar tacks.
    if you don't have a machine, it probably wouldn't be to hard to find someone to sew it for you.
    don`t leave the CREATOR out of the creation!

  3. #3
    Senior Member blackbishop351's Avatar
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    Quote Originally Posted by Curt View Post
    Here's what I've gathered so far for a hammock that balances strength and low weight. I'm not worrying about the bug netting or fly for now - just the hammock.

    I need it to support 400 pounds. Unlikely to ever actually have that much in it, but me (big), my kid (little), and stuff could come close. It builds in a safe margin of error and seems to be a common number (Travel Hammock, ENO, etc.)

    So....

    Hammock fabric: 1.9oz ripstop nylon - buy 4 yards of 60-63". Use full width (halfway between a single and a double). Use 10 or 11 feet of length depending on how I do the ends. Make a few side pockets from the extra
    How do you plan on attaching the side pockets? I ask because stitching in the body of a hammock can be iffy. Jeff and Risk have done it with no problems, but I've heard of others getting dropped on their butts. I personally wouldn't try it. Side pockets could just be sewn into the hammock hem though, as long as the sides of the hammock itself are kept tight enough. IMO storage that suspends from the ridgeline or supports is a more solid way to go.

    Quote Originally Posted by Curt View Post
    Tree straps: 1.5" webbing. Probably Speer's version. Nice and long to get around the Pacific Northwest's big trees. Do people just tie a loop in the end and run it through like a girth hitch?
    I agree with slowhike here. I wouldn't trust a knot in webbing. Technically Ed Speer uses a knot to hang his hammocks, but it's really more of a lashing. Sewing loops into the webbing is definitely a better way to go IMO. I will disagree on a minor point, though - I've had bartacked webbing drop me before. I use a double box stitch now, with a light bartack on each end. No problems with that....at least not yet

    Quote Originally Posted by Curt View Post
    Rope/cord: 5mm seems to be strong enough for big loads with some room to spare. Rated to 1100 or 1200 lbs. Put a bight on the end and carabiner it to the webbing?
    Don't go by the size of the cord, go by a listed rating. The size really has nothing to do with it. I have 1/2" utility cord around the house that's only rated to ~ 500 lbs., but I use 1/8" Spyderline (mentioned by TeeDee) on my hammocks that's rated to ~ 1200 lbs. Also, for a ~400 lb. load, you'll want something stronger. At a 20* sag angle and 400 lbs., you're getting right to the limit of a 1200 lb. rated suspension. I'd definitely go up a rating jump to allow for error; 2000 lbs. rating would be sufficient for me to feel safe in that situation.

    Something else you might really want to consider on a DIY hammock is a structural ridgeline. Hennessy is the only guy who sells these - because he patented the idea and won't let anyone else use it - but you're completely free to put them on your own hammocks or add them to hammocks you've bought. A ridgeline gives you storage options, holds up a variety of sock/pod type devices, and lets you hang your hammock with exactly the same sag every time, rather than having to "guesstimate" on each hang.
    "Physics is the only true science. All else is stamp collecting." - J. J. Thompson

  4. #4
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    Hey Curt,

    I'm definitely the least experienced responder thus far, but man, I'm thinking the fabric is the weak link in the equation. (I'm flying around right now with a cheapie 20 buck Travel Hammock Ultralite in a cargo plane in turbulence, and although it creaks under stress, no hint of fatigue anywhere...) Webbing or rope, a bowline looped in a Girth Hitch (my mainstay) seems more than strong enough to hold most anyone that's not famous for being overweight. Or, I'm guessing, even a burly dad & a couple kids or a really big dog. If you don't swing in it like I did in the scouts (We managed to pop a rope in one of those old net hammocks, going at least 90 degrees per swing), you'll probably be ok!

  5. #5
    Senior Member blackbishop351's Avatar
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    Quote Originally Posted by robertm View Post
    Hey Curt,

    I'm definitely the least experienced responder thus far, but man, I'm thinking the fabric is the weak link in the equation. (I'm flying around right now with a cheapie 20 buck Travel Hammock Ultralite in a cargo plane in turbulence, and although it creaks under stress, no hint of fatigue anywhere...) Webbing or rope, a bowline looped in a Girth Hitch (my mainstay) seems more than strong enough to hold most anyone that's not famous for being overweight. Or, I'm guessing, even a burly dad & a couple kids or a really big dog. If you don't swing in it like I did in the scouts (We managed to pop a rope in one of those old net hammocks, going at least 90 degrees per swing), you'll probably be ok!
    I might tend to disagree...because of the way the forces are dissipated over the surface of the fabric, the only spot you should have to worry about is right under your butt - a force focus. I think 1.9 oz. ripstop is probably more than strong enough for a really heavy person. That's just me, though.

    Be careful with suspensions. The tension you exert on your suspension lines can be many, many times your body weight, depending on the sag angle you use. There have been many reports of guys trying substandard materials for suspensions and falling on their butts...just ask around.
    "Physics is the only true science. All else is stamp collecting." - J. J. Thompson

  6. #6
    Senior Member Curt's Avatar
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    TeeDee,

    Great link! Looks like some insanely light stuff. Does Dyneema handle UV well?

    I'll put together the different info I'm finding on weights and strength. I'll post it to double-check with all you experts before making purchases. Thanks again!!

    -Curt

  7. #7
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    For reference I currently use 1.9 ripstop nylon dwr, 11' long, 60" wide. I weigh about 280lb. There has been no evidence of stretch or stress tears in the 6 weeks I've been using the hammock on a constant basis.

    I've also tested using 2 layers of 1.1 ripstop nylon, 9' long, 60" wide. Me and a friend spent about 2 hours in this one at a combined weight of around 550lb. I'm using 1" Polyester webbing for the supports. It seemed to hold up pretty well.

    Neither of the hammocks were hemmed or heat sealed on the edges.
    Last edited by spchtr; 05-28-2007 at 15:58. Reason: ps.

  8. #8
    Senior Member Curt's Avatar
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    Quote Originally Posted by spchtr View Post
    For reference I currently use 1.9 ripstop nylon dwr, 11' long, 60" wide. I weigh about 280lb. There has been no evidence of stretch or stress tears in the 6 weeks I've been using the hammock on a constant basis.

    I've also tested using 2 layers of 1.1 ripstop nylon, 9' long, 60" wide. Me and a friend spent about 2 hours in this one at a combined weight of around 550lb. I'm using 1" Polyester webbing for the supports. It seemed to hold up pretty well.
    Dang! Now that's a test! Were these knotted at the ends? Whipped and tied? If you had to compare the 1.9 vs two layers of 1.1, which do you think would be stronger? I like the idea of a double bottom and the math would lead me to think the two 1.1 would be stronger, but I'm curious about the real world use.

    Thanks for the helpful post!

    -Curt

  9. #9
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    Quote Originally Posted by Curt View Post
    Here's what I've gathered so far for a hammock that balances strength and low weight. I'm not worrying about the bug netting or fly for now - just the hammock.

    I need it to support 400 pounds. Unlikely to ever actually have that much in it, but me (big), my kid (little), and stuff could come close. It builds in a safe margin of error and seems to be a common number (Travel Hammock, ENO, etc.)

    So....

    Hammock fabric: 1.9oz ripstop nylon - buy 4 yards of 60-63". Use full width (halfway between a single and a double). Use 10 or 11 feet of length depending on how I do the ends. Make a few side pockets from the extra

    Tree straps: 1.5" webbing. Probably Speer's version. Nice and long to get around the Pacific Northwest's big trees. Do people just tie a loop in the end and run it through like a girth hitch?

    Rope/cord: 5mm seems to be strong enough for big loads with some room to spare. Rated to 1100 or 1200 lbs. Put a bight on the end and carabiner it to the webbing?

    Am I on the right track? Will that hold me up - assuming construction methods are appropriate and done right?

    Thanks!

    -Curt
    Na dude. You said 400 lbs? Are you and your kid going to be sleeping in the same hammock. If so, that's a bad idea. Just make two hammocks: one for you and one for your kid. The kid can learn some valuable skill in knot tying by having his own hammock.

    I would go with Polyester webbing. 3500 lbs breaking strength. You gonna need it if you've got 400 lbs to support. I used polester webing for a year and it finally started tearing around the rings. So I upgraded to polyester. Polyester doesn stretch anywhere near as much as polypro.

    Also forget 1200 strength rope go ahead get the 1900 lbs stuff or above.

    Fabric? I'd use two layers of 1.9 ounce ripstop. Your talking 400 lbs here man, not 250 or 260 lbs.

    If you want to stay alive, overengineer the thing. Then try to cut down weight.
    Last edited by funbun; 05-29-2007 at 12:24.

  10. #10
    Senior Member Just Jeff's Avatar
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    My youngest sleeps with me in my hammock all the time. We don't add up to 400 lbs, though.
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